How do you get through the radiation pit surrounded by supermutants in fallout 3?

OK, there's this spot in fallout 3 that is north of little lamplight. It's on the wasternside of the world map in your pip boy. when i walk north from little lamplight, i find this groove with supermutants all around it. If i try to walk into it, there's this radioactive gas that gives you 1,000 RADS per secound!!! (About .5 Secounds of exposure will kill you) HOWEVER, my world map says that there is an undiscovered location INSIDE the gas of death. I CAN see a gate to something inside the gas, but i can't even get close to it without dying of radiation poisoning. SOOOO my question is, ho do you get through it? (I've tried popping 60 (literally) Rad-x's and wearing a radiation suit, but i still die. HELP ME!